
reproduce-bug
Reproduce a bug from a Linear ticket with a failing test. Expects the full ticket context (title, description, comments) to be provided as input.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/n8n-io/n8n --skill reproduce-bug- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads reproduce-bug automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Bug Reproduction Framework
Given a Linear ticket context ($ARGUMENTS), systematically reproduce the bug with a failing regression test.
Step 1: Parse Signals
Extract the following from the provided ticket context:
- Error message / stack trace (if provided)
- Reproduction steps (if provided)
- Workflow JSON (if attached)
- Affected area (node, execution engine, editor, API, config, etc.)
- Version where it broke / last working version
Step 2: Route to Test Strategy
Based on the affected area, pick the test layer and pattern:
| Area | Test Layer | Pattern | Key Location |
|---|---|---|---|
| Node operation | Jest unit | NodeTestHarness + nock | packages/nodes-base/nodes/*/test/ |
| Node credential | Jest unit | jest-mock-extended | packages/nodes-base/nodes/*/test/ |
| Trigger webhook | Jest unit | mock IHookFunctions + jest.mock GenericFunctions | packages/nodes-base/nodes/*/test/ |
| Binary data | Jest unit | NodeTestHarness assertBinaryData | packages/core/nodes-testing/ |
| Execution engine | Jest integration | WorkflowRunner + DI container | packages/cli/src/__tests__/ |
| CLI / API | Jest integration | setupTestServer + supertest | packages/cli/test/integration/ |
| Config | Jest unit | GlobalConfig + Container | packages/@n8n/config/src/__tests__/ |
| Editor UI | Vitest | Vue Test Utils + Pinia | packages/frontend/editor-ui/src/**/__tests__/ |
| E2E / Canvas | Playwright | Test containers + composables | packages/testing/playwright/ |
Step 3: Locate Source Files
Find the source code for the affected area:
- Search for the node/service/component mentioned in the ticket
- Find the GenericFunctions file (common bug location for nodes)
- Check for existing test files in the same area
- Look at recent git history on affected files (
git log --oneline -10 -- <path>)
Step 4: Trace the Code Path
Read the source code and trace the execution path that triggers the bug:
- Follow the call chain from entry point to the failure
- Identify the specific line(s) where the bug manifests
- Note any error handling (or lack thereof) around the bug
Step 5: Form Hypothesis
State a clear, testable hypothesis:
- "When [input/condition], the code does [wrong thing] because [root cause]"
- Identify the exact line(s) that need to change
- Predict what the test output will show
Step 6: Find Test Patterns
Look for existing tests in the same area:
- Check
test/directories near the affected code - Identify which mock/setup patterns they use
- Use the same patterns for consistency
- If no tests exist, find the closest similar node/service tests as a template
Step 7: Write Failing Test
Write a regression test that:
- Uses the patterns found in Step 6
- Targets the specific hypothesis from Step 5
- Includes a comment referencing the ticket ID
- Asserts the CORRECT behavior (test will fail on current code)
- Also includes a "happy path" test to prove the setup works
Step 8: Run and Score
Run the test from the package directory (e.g., cd packages/nodes-base && pnpm test <file>).
Classify the result:
| Confidence | Criteria | Output |
|---|---|---|
| CONFIRMED | Test fails consistently, failure matches hypothesis | Reproduction Report |
| LIKELY | Test fails but failure mode differs slightly | Report + caveat |
| UNCONFIRMED | Cannot trigger the failure | Report: what was tried |
| SKIPPED | Hit a hard bailout trigger | Report: why skipped |
| ALREADY_FIXED | Bug no longer reproduces on current code | Report: when fixed |
Step 9: Iterate or Bail
If UNCONFIRMED after first attempt:
- Revisit hypothesis — re-read the code path
- Try a different test approach or layer
- Maximum 3 attempts before declaring UNCONFIRMED
Hard bailout triggers (stop immediately):
- Requires real third-party API credentials
- Race condition / timing-dependent
- Requires specific cloud/enterprise infrastructure
- Requires manual UI interaction that can't be scripted
Output: Reproduction Report
Present findings in this format:
Ticket: [ID] — [title] Confidence: [CONFIRMED | LIKELY | UNCONFIRMED | SKIPPED | ALREADY_FIXED]
Root Cause
[1-2 sentences explaining the bug mechanism]
Location
| File | Lines | Issue |
|---|---|---|
path/to/file.ts | XX-YY | Description of the problem |
Failing Test
path/to/test/file.test.ts — X/Y tests fail:
test name— [failure description]
Fix Hint
[Pseudocode or description of the fix approach]
Important
- DO NOT fix the bug — only reproduce it with a failing test
- Leave test files in place as evidence (don't commit unless asked)
- Run tests from the package directory (e.g.,
pushd packages/nodes-base && pnpm test <file> && popd) - Always redirect build output:
pnpm build > build.log 2>&1 - DO NOT look at existing fix PRs — the goal is to reproduce from signals alone
FAQ
What does the reproduce-bug skill do?
Reproduce a bug from a Linear ticket with a failing test. Expects the full ticket context (title, description, comments) to be provided as input.
How do I install reproduce-bug?
Run npx skills add https://github.com/n8n-io/n8n --skill reproduce-bug in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/reproduce-bug/ (personal) or .claude/skills/reproduce-bug/ (project).
Which AI agents can use reproduce-bug?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is reproduce-bug safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains reproduce-bug?
It is published by n8n-io in n8n-io/n8n, and it is an official skill from the maker of the technology it covers. It has 306 recorded installs.
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